1. Field of the Invention.
The present invention relates to a method and apparatus for providing self-aligning connections for a two section mast for a drilling rig.
2. Prior Art.
In various oil and gas operations, well drilling rigs are utilized for subterranean drilling. A mast or derrick of a drilling rig are well known devices used in oil and gas and other drilling operations. The drilling rig will often include an upstanding mast connected to the floor of the drilling rig. The mast may extend vertically 40 to 50 meters or more and be composed of structural steel framework.
It is often desirable to move a large drilling rig, including all of its equipment, from one well bore to another. In the past, in order to move a large drilling rig, it has been necessary to disassemble or “rig down” the drilling structure. The rig down process requires a great many steps including disconnecting all ancillary services, laying down of the mast from a vertical to a horizontal position, disassembling the mast, moving the drilling structure components to an alternate well bore, and then reassembling the entire drill structure in a “rig up” operation.
The drilling mast may include a back face joining a pair of sides and an open front face. The mast may be divided into a top mast section and a bottom mast section, with each mast section having front legs and rear legs. Each mast section may be brought to a well site on a vehicle and then the front legs and the rear legs of the sections are attached.
Once the sections of the mast are connected together while in a horizontal position, the mast would be moved radially from a horizontal to a vertical position.
When connecting the sections of mast together, it is necessary to align the connecting ends of the legs and insert pins through aligned openings to hold the sections together. This typically would require repeated movements of the sections until they were positioned in proper alignment. Even with repeated movements of the mast sections, there would be required extensive use of sledge hammers or other equipment to drive the pins in.
Also in the past, the concept of self aligning connections in which structural components are maneuvered into final position by guiding elements has been utilized and is common within many industries. In fact, at least one prior drilling mast utilizes a self aligning type connection to join a fixed lower section to an upper section that is lifted into position by a crane.
However, the present invention is unique in the configuration and geometry of the structural/guiding elements and in the process by which an upper mast section is positioned in a generally horizontal plane by a tractor trailer with dolly and then aligned and joined by the connection to a fixed lower mast section supported at one end by hydraulic mast stands.
Accordingly, it would be advantageous to provide a two section mast with self-aligning connections which reduces the number of truck loads required for moving the sections and which improves the overall efficiency of the rig up and rig down process.
It would also be advantageous to provide a two section mast with self-aligning connections which eliminates complicated and cumbersome systems required in telescopic, folding, or collapsible mast designs.
It would also be advantageous to provide a two section mast with self-aligning connections which reduces the time required for mast assembly prior to erection by repeatable and precise relative positioning of the mast sections with respect to each other.
It would be advantageous to provide a two section mast with self-aligning connections which facilitates controlled pin installation rather than sledge hammer driven alignment.
It would be advantageous to provide a two section mast with self-aligning connections which reduce or eliminate the use of sledge hammers during mast assembly and disassembly.